A refractory gold ore is naturally resistant to recovery by cyanidation and carbon absorption processes.
This kind of gold ore has particles covered with sulfide minerals that prevent contact between the cyanide leach solution and gold particles.
The Metallurgical Technology Division (MeTD) of the bureau is conducting a research on the isolation and propagation of the bacteria Thiobacillus ferrooxidans and Thiobacillus thiooxidans to be used for bioleaching.
Bioleaching is the extraction of metal from ore through the use of living microorganisms. It is one of the pre-treatment processes resorted to when standard techniques such as straight cyanidation leaching is not feasible.
This pre-treatment removes the unwanted materials enveloping the precious metal prior to actual cyanidation.